Hydrocatalytic refining of lubricating oils and catalyst therefor



United States Patent HYDROCATA'LYTIC :REFI'NIN G OF'LUBRICATING OILS ANDCATALYST THEREFOR Hillis 0. Folkins, Crystal Lake, Elmer L. Miller,Cary,

and Charles T. OMalley, Chicago, Ill., assignors to Ellie. Pure OilCompany, "Chicago llhfa corporation of No Drawing. ApplicationMay14,1957 Serial No. 658,957

5 Claims. (Cl. 208-264) This invention relates to a process for refiningor finish-treating lubricating oils or their fractions by hydrogenationunder specific mild conditions, in the presence of a catalyst comprisingmolybdenum oxide on a siliceous support, wherein improvements inphysical properties of theproducts are obtained without impairment ofthe inherent good qualities of the feed oil. More particularly, theprocess is one in which, through mild hydrogenation using a particularcatalyst, improvements in such properties as steam emulsion number andreduction in neutralization number are obtained without reduction in thecontent of naturally-occurring inhibitors present in the lubricating'oil feed.

Recent developments in the hydrogenation of petroleum show that it isadaptable for converting fuel oil to gasoline and gas oil, increasingthe parafiinicity of kerosenes, burning oils, and lubricating oils, andconverting all types of asphalts =to distillate fuels. Until the lastfew years, commercial hydrogenation has been restricted to the use .ofhighly purified hydrogen at pressures greater than atmospheric,temperatures below decomposition temperaturesof the feed, andin thepresence of powerful but sensitive catalysts of 'the type .of reducednickel. These processes are generally applicable tosulfur-free andarsenic-free materials, and accordingly are related primarily .tothetreatmentof vegetable fats and oils. By using hydrogen alone andemploying greatly increased pressures, both .coal and .petroleum oilscan be highly liquefied, but because of their high contents of sulfur,oxygen compounds :and ring-type-compounds the resulting products arediflicult to crack or further: refine. With the advent oficatalyticdesulfurization, hydrogenation and reforming processes as applied tolighter stocks, and the developmenttof sulfur resistant catalysts, thearthas seen many developmentsin the field of flexible methods oftreating and refining by the use of hydrogen.

Refming through the use of both chemical and physical means has longbeen known to enhance the utility and stability of waxes, lubricatingoils andiheir fractions. In the application of hydrogenationas therefiningmethod, the artlists alarge number of metal compounds,particularly the oxides and sulfides of the metals of group VI and groupVIII, paying particular attention to nickel,cobalt, iron, molybdenum,tungsten and chromiumiforwthese purposes. It is also recognized in the.art .that only through judicious application of refining methodscantheinherent stability, color properties, or viscosity-temperaturecharacteristics of a :lubricating oil --0r wax be preserved, since manyrefining operations, including acid treatment, hydrogenation, solventextraction, adsorption, thermal diffusion, extractive distillation,Ihydrodesulfurization, and chemical and-clay treatments,.removedesirable constituents along withthe undesirable constituents. Toovercome the shortcornings of the refining methods, it is=commonpracticeto incorporate various addends in the finished products and about newproperties. Thus, it is common practice to apply refining methods to theextent of their worth as-regards-enhancement of viscosity,viscosity-index, color and carbon residue and then fortify the finishedoil by the use of addends to offset deficiencies in oxidation stability,demulsibility, acid number, sludge "resistance and the tendency tocorrode metal parts which are directly or indirectly a result of therefining process.

Within the vast amount of art available on hydrogenation,hydrodesulfurization, destructive hydrogenation (hydrogenolysis) andrelated refining processes employing hydrogen to treat a wide variety offeed stocks, attention is generally directed to such matters andproblems as the method of catalyst preparation or pretreatment, catalystcomposition, removal or destruction of sulfur, oxygen and nitrogencompounds, removal or destruction of asphaltic or resinous compounds,the use of promoters in obtaining fiuidizable catalysts, color stabilityin the product, removal of unsaturates and maintaining catalyst life oractivity. These processes are generally conducted at temperatures above750 F., employing pressures well above 500 lbs. per square inch, and assuch inherently remove or transform both the undesirable and thedesirable constituents therein. The art has now come to recognize thatcertain of'the naturally-occurring sulfur, oxygen and nitrogencompoundsthat are destroyed or removed during these refining operations,have a decided effect upon the oxidation stability and sludge-formingpropensities of the refined lubricating oils. A finished lubricatingoil, consisting as it does of 10 to 40% of high boiling aromaticcompounds, 25 to 80% of 'naphthenic hydrocarbons, and 15 to 75% ofisoparafiinic hydrocarbons, along with various percentages of sulfur,oxygen and nitrogen compounds, represents a complex system for study.Although it is recognized that the stability of the lubricating oil inservice, wherein it is subjected to-highly complicated oxidationatmospheres catalyzed by the presence of metallic surfaces,whichoxidation progresses as the extent of use is prolonged, may be improvedby removing certain of the more unstable naphthenes, aromatics, ordiphenyls, the organic sulfur compounds are responsible for much of theremaining resistance to oxidation the oil may have.

Attempts havebeen made to isolate the sulfur compounds naturally presentin lubricating oil fractions, as by the formation of mercuric chlorideaddition com- ,pounds, or by selective adsorption on fullers earth, but

the results'werenot quantitative and the sulfur-rich extracts proved tobe intractable'and could not be separated or purified by ordinarychemical means. In many .instances, 'it has 'been reported that thesulfur-containing fractions did not inhibit the oxidation of thesulfur-free oils. The-sulfur compounds themselves must be as complicatedasthe mixtures of hydrocarbons'fro-m which they are extracted. Researchon the oxidation inhibition qualit-iesof synthesized sulfur compoundshas indicatedthat monosulfides are good inhibitors; those sulfurcompounds in which the sulfur is a part of a ring are somewhat moreactive, but mercaptans and disulfides are not as active on an equivalentsulfur basis as the corresponding monosulfides. These differences arepartly attributed to the in- .fiuence .of therate of reaction .of thesulfurcompounds with peroxides formed or present in .oiL-andit isgenerally accepted that the rate of oxygen adsorptioniof oils may beproportional to the peroxide concentration. Thoseioils which containnatural antioxidants, or agents :oapableof reducing peroxides, will notbuildup high peroxide concentrationswith consequent high oxidationrates. Sulfur-compounds in their reaction withthe peroxidesareoxidizedto deleterious products inthe oil. The'refiner,

concentrations of peroxides and consequent high oxidathe viscosity,viscosity-index, color and other related properties without adverselyafiecting the steam emulsion number or destroying thenaturally-occurring oxidationinhibiting sulfur compounds, while at thesame time attacking the oxygen-containing compounds to the extent thatthe content of naphthenic acids is reduced sufiiciently to meet therequired neutralization number.

Accordingly, a first object of this invention is to provide a processfor refining or finishing lubricating oil fractions and lubricating oilbase stocks.

Another object of this invention is to provide a superior catalystcomposition and method of its utilization for improving the propertiesof lubricating stocks by mild hydrogenation.

A third object of the invention is to provide a catalyst for the mildhydrotreating of lubricating oils, which catalyst contains a minoramount of an oxide of molybdenum incorporated on a silica-aluminasupport containing a predominant amount of silica.

Still another object is to provide a process for preparing neutrals orlubricating oil stocks of lower density and other improved propertiesfrom heavier stocks such as deasphalted oils and bright stocks.

These and other objects of the invention will become apparent as thedescription thereof proceeds.

In order to demonstrate the invention, a series of experiments wereconducted in which a 241 viscosity neutral lubricating oil stock wastreated to mild hydrogenation at diiferent temperature levels at aliquid volume hour space velocity of 1.5, hydrogen-to-oil mol ratio of6.5 to 7.5, and under a pressure of 500 p.s.i.g., employing variousmolybdena-containing catalysts. The lubricating oil before treatment hadthe following characteristics:

The results of these experiments are shown in the following table:

From the results shown in the table it is seen that in runs No. 3, 6 and7 the products have increased viscosity index and exhibit propertieswhich show controlled hydrocracking. Reference is made to the last threecolumns of the table which show the amount of material boiling below theinitial boiling point of the charge, the viscosity index of the productfraction having an initial boiling point of 718 F. (the initial B.P. ofthe charge), and the initial boiling point of the hydrogenated product.Although all of the runs were conducted at a low space velocity of 1.5,the data at 650 F. indicates that this temperature is the highesttemperature desirable for the reaction. The acid reduction was not asgood at 650 F. as that obtained at 550 F., and at the highertemperature, desulfurization is becoming appreciable. At these highertemperatures the controlled hydrocracking is increased and therefore theactive cycle life of the catalyst is shorter. This necessitatesintermittent catalyst regeneration in order to maintain catalystactivity at the maximum if charge stocks are employed whereinsubstantial lowering of viscosity is desired. Otherwise, the catalystwill perform to quantitatively remove acids but the extent of controlledhydrocracking will be reduced. It should be noted also that at 650 F.the improvement in steam emulsion characteristics has passed theoptimum, although results are obtained which are still far superior tothose obtained under any conditions over catalysts composed ofmolybdenum oxide on alumina, or molybdenum oxide on alumina which hasonly small amounts of silica incorporated therein.

In another series of runs, several catalysts were tested over a longerperiod of time in order to determine their relative efliciencies forremoving acids from the 241 viscosity neutral lubricating oil stock usedin the runs presented in Table 1. Before making these runs the catalyststested were calcined and reduced at around 800 F. Runs were made at apressure of 250 p.s.i.g., and at temperatures of around 570 F. Thecharge rates were at a LVHSV of 1.3 and the hydrogen charge rate was3000 cubic feet per barrel of charge. After 15 hours on stream, the acidnumbers as shown in Table II were obtained. These results clearly showthe superiority of the catalyst of our invention under conditions ofmild or incomplete pretreatment or regeneration procedures. Under morecomplete regeneration procedures at temperatures of around 1000 F.,complete acid removal is obtained over each of the catalysts forprolonged cycles of operation. The data thus show that the catalyst ofour invention is less dependent upon precise regeneration proceduresthan are other compositions.

The data show that catalysts containing 3.0 to 10% M00 onsilica-alumina, high-surface-area supports containing around 83 toaround 90 percent silica are far superior to other catalyst compositionswhen used in the temperature range of 550-650 F., and that beyond thesetemperature ranges the catalysts still function although they arerelatively less superior at higher temperatures.

TABLE I Hydrotreating lubricating oil Catalyst Composl- Characteristicsof Product tlon Tengp.

0 IBP Run treat- No. Per- Base Comp. ment, Vis., SUS Wt Steam Vol. VIovercent F. API Color 0. R. an" M01 N eut. VI Per- Emul- Percent Lubehead M 0 Wt. N 0. cent 51011 71 Stock S102 A120: 100 F. 210 F. S No. F

In orderto show the influenceof temperature on the properties ofproducts-obtained over these catalysts, a run was carried out at 700 F.using 2'4'1 viscosity neutral lubricating oil stock as the charge andmaintaining other operating conditions the same as in the above runs.Using the 10 percent M on a silica-alumina support, containing 17percent alumina, a product of the following properties was obtainedduring a run of 1-9-hours du- TABLE II Charge Product; Catalystomposition, Neutralizaperm Neut. No. 1948) -Q 1.51 .03 it??? 5 as. a.MOO5 -Sz A1203 9.0 1.0 99.0 0 Considerable controlled hydrocracking wasachieved. 8:8 3- 3 8:52 Thus the data show that the combination of about10 10% M00 on 87% SiO and 13% A1 0 as the catalyst, used at temperaturesof 550650 F., gives the best The superiority in the prescribedtemperature range is results. Othercatalyst"compositions, even when usedat readily seen by comparing the catalysts of runs 3-and 5 the criticaltemperature range, either fail to give the re 'dfTable I. The catalystof -run 3 produces aniincreascd quired reduction in neutralizationnumber, reduce the API gravity, preferred controlled hydrocracking,andin 15 naturally-occurring sulfur compounds, or unduly infiucreasedviscosity characteristics. On the other hand, the ence thesteamemulsion-number of the product. catalyst of run 5 does little morethan efifect acid re- The invention may be applied to any lubricatingoil or moval. Steam emulsion characteristics are vastly irnfractionthereof. Both-neutrals and bright stocksmay; be proved with thecatalystof run 3, whereas in run 5 the satisfactorily treated inaccordance with the invention. improvement-is of far lesser magnitude.The process may be advantageously applied to the conversion .of brightstocks into neutrals by mild hydrogenation, and maybeapplied wherethemain objectof the treatment is areduction in the viscosity of thelubricating oil and an increase in viscosity index without affecting thesulfur content and without producing gas or gasoline. The inventionalso-finds use where reduction of steamemulsionnumber is theprimaryobject, as in the development of steamzturbine oils. The following Tableration: III sets forth the physical properties of some lubricating TABLEIII Hydrogenation charge oils SUS Viscosity Total Conrad- No.Description VI Neut.No. API srlrfir, son Vail I 100 F. 210 F. PercentPercent Heavy deasphalted oil 0.80 22. 9 1.87 Medium neutral distillate2. 9 24. 2 1.13 0. 11 do 2. 9 24. 0 1.13 0. 05 Heavy deasphalted oil0.85 22. 5 1.10 2.0

Medium neutral distillata..- 3.03 24. 3 1.15 0.07 Heavy deasphaltedoil 1. 6 21. 6 1. 23 2. 23 Neutral distillate 3. 03 24. 2 1. 13 Heavydeasphalted re duum 1. 51 21.7 1.14 1.96 do 1.64 1.23 2.0

Solvent-refined neutral dist 0. 15 34. 0 0.12 0.01 do 0.30 28.6 0.450.02 do 0. 27.0 0.60 0. 25 Solvent-refined bright stock--- 0.25 26. 5 0.0.60 -do 0. 45 24. 3 0.75 1. 2

API gravity 25.3 oils that may be benefited by applying the mildprocess- Vis., SUS 100 F 197.0 ing with hydrogen according to thisinvention. Vis. SUS 210 F 45.2 In general, the operating conditions usedin treating Viscosity index 80.0 lubricating oils to obtain the desiredresults are as fol- Neut. No. (1948) 0.0 lows: Sulfur, wt. percent 0.87TABLE IV 1 Color NPA 2/2 Temperature, F 500-650 It is thus seen thatwhile these results are equal or supe- LVHSV rior to those obtained overcatal sts consistin of molyb- Hydogen/HC ratlo 5'0 10 y g Pressure, p.si g 250-600 denum oxide on supports consisting essentially of alumina,the results are inferior to those obtained over the same preferredcatalysts at lower temperatures, i.e., runs 3, 6 and 7 of Table I, andthat by operating at the higher temperatures much of the superioractivity of the preferred catalysts is lost.

The efiiciency of these catalysts for other stocks also has beendemonstrated. A deasphalted oil was processed over a catalyst composedof 10 percent molybdenum oxide on a support of 83/ 17 SiO /Al O toremove acids at 595 F., 250 p.s.i.g., a LVHSV of 1.5, and a hydrogenrate of 2400 cubic feet per barrel of charge. The following results wereobtained:

By operating within the conditions set forth in Table IV using acatalyst composition consisting of about 3% molybdenum oxide, about 87%silica and 13% alumina with trace amounts of Na O, Fe O and other tracematerials, lubricating oil distillates, bright stocks, and deasphaltedresidual oils can be improved with respect to their VI, color,neutralization number, demulsibility, and content of carbon residue,resins and oxygenated com pounds, without impairment of the naturallyoccurring sulfur content. In addition to this, where subsequent refiningoperations are to be employed, such as extraction, it will be found thatthere is a decrease in corrosion with- 7 in the extraction system andeconomies are obtained in the finishing clay-contacting treatments. Thecatalyst composition is subject to very little variation; in general, aminimum of about 2.5 to 3.5 weight percent of molybdenum oxide must bepresent with the upper limit at about 10 Weight percent and thesiliceous support must contain between about 83 and 90% silica, whichmeans that the alumina content can vary between 10 and 17%.

What is claimed is:

1. The process of refining mineral lubricating oils having naturalresistance to oxidation and deterioration due to the content ofnaturally-occurring sulfur compounds therein and containing acidiccompounds whereby the viscosity and viscosity index characteristics ofsaid lubricating oils are enhanced, the steam emulsion number reducedand the content of said acidic compounds reduced without affecting thecontent of said naturallyoccurring sulfur compounds which consists insubjecting said mineral lubricating oils to contact with hydrogen at atemperature of between about 550 and 650 F. in the presence of acatalyst selected from the group consisting of a silica base containingabout 87.0 wt. percent of silica and about 13.0 wt. percent of aluminawith about 3.0 wt. percent of molybdenum oxide, a silica base containingabout 83.0 wt. percent silica and about 17.0 wt. percent of alumina withabout 10.0 wt. percent of molybdenum oxide and a silica base containingabout 87.0 wt. percent silica and about 13.0 wt. percent alumina withabout 10.0 wt. percent of molybdenum oxide, and recovering ahydrogenated lubricating oil characterized by having an improvedviscosity index and 8 reduced neutralization number Without reduction ofsaid naturally-occurring sulfur compounds and without impairment of thephysical properties thereof.

2. The process in accordance with claim 1 in which said catalystconsists in a silica base containing about 87.0 wt. percent of silicaand about 13.0 wt. percent of alumina with about 3.0 wt. percent ofmolybdenum oxide.

3. The process in accordance with claim 1 in which said catalystconsists in a silica base containing about 83.0 wt. percent of silicaand about 17.0 wt. percent of alumina with about 10.0 wt. percent ofmolybdenum oxide.

4. The process in accordance with claim 1 in which said catalystconsists in a silica base containing about 87.0 wt. percent of silica,and about 13.0 wt. percent of alumina with about 10.0 wt. percent ofmolybdenum oxide.

5. The process in accordance with claim 1 in which the minerallubricating oil is selected from the group consisting of heavydeasphalted oil, medium vis. distillate oils, solvent-refined neutraldistillates and solvent-refined bright stocks.

References Cited in the file of this patent UNITED STATES PATENTS2,654,696 La Porte Oct. 6, 1953 2,706,167 Harper et al. Apr. 12, 19552,787,582 Watkins et a1. Apr. 2, 1957 2,799,626 Johnson et al. July 16,1957

1. THE PROCESS OF REFINING MINERAL LUBRICATING OILS HAVING NATURALRESISTANCE TO OXIDATION AND DETERIORATION DUE TO THE CONTENT OFNATURALLY-OCCURRING SULFUR COMPOUNDS THEREIN AND CONTAINING ACIDICCOMPOUNDS WHEREBY THE VISCOSITY AND VISCOSITY INDEX CHARACTERISTICS OFSAID LUBRICATING OILS ARE ENHANCED, THE STEAM EMULSION NUMBER REDUCEDAND THE CONTENT OF SAID ACIDIC COMPOUNDS REDUCED WITHOUT AFFECTING THECONTENT OF SAID NATURALLYOCCURRING SULFUR COMPOUNDS WHICH CONSISTS INSUBJECTING SAID MINERAL LUBRICATING OILS TO CONTACT WITH HYDROGEN AT ATEMPERATURE OF BETWEEN ABOUT 550* AND 650*F. IN THE PRESENCE OF ACATALYST SELECTED FROM THE GROUP CONSISTING OF A SILICA BASE CONTAININGABOUT 87.0 WT. PERCENT OF SILICA AND ABOUT 13.0 WT. PERCENT OF ALUMINAWITH ABOUT 3.0 WT. PERCENT MOLYBDENUM OXIDE, A SILICA BASE CONTAININGABOUT 83.0 WT. PERCENT SILICA AND ABOUT 17.0 WT. PERCENT OF ALUMINA WITHABOUT 10.0 WT. PERCENT OF MOLYBDENUM OXIDE AND A SILICA BASE CONTAININGABOUT 87.0 WT. PERCENT SILICA AND ABOUT 13.0 WT. PERCENT ALUMINA WITHABOUT 10.0 WT. PERCENT OF MOLYBDENUM OXIDE, AND RECOVERING AHYDROGENATED LUBRICATING OIL CHARACTERIZED BY HAVING AN IMPROVEDVISCOSITY INDEX AND REDUCED NEUTRALIZATION NUMBER WITHOUT REDUCTION OFSAID NATURALLY-OCCURRING SULFUR COMPOUNDS AND WITHOUT IMPAIRMENT OF THEPHYSICAL PROPERTIES THEREOF.